ginger zee on a very festive columbus avenue right here in new york tonight. ginger, thank you. >>> to other news this evening and to that political bombshell. a well-known congressman resigning today. jesse jackson, jr. after months of federal investigations, medical treatments and then a win on election day, today, an unexpected turn. here's abc's sharyn alfonsi tonight. >> reporter: once a political rising star, jesse jackson, jr. today called it quits, sending in a letter of resignation to house speaker john boehner. he wrote, "over the past several months as my health has deteriorated, my ability to serve the constituents of my district has continued to diminish." the drama around jackson began this summer when the congressman disappeared for weeks. the public, even members of his staff, didn't know where he was. finally, in late july, the mayo clinic revealed jackson was being treated there for what was later diagnosed as bipolar disorder and depression. his famous father uncharacteristically quiet about the matter. >> the fact is, the congressman is und